Magnetic recording medium, method of manufacture therefor, and magnetic read/write apparatus

ABSTRACT

A magnetic recording medium having excellent magnetic read/write characteristics and thermal stability characteristics, and a method of manufacturing therefor, and a magnetic read/write apparatus are provided. This magnetic recording medium comprises an orientation control film  3  that controls the orientation of a film provided directly thereabove, a perpendicular magnetic film  5,  of which the axis of easy magnetization is generally oriented perpendicular to a substrate, and a protective film  6,  that are provided on a non-magnetic substrate  1,  wherein the orientation control film  3  is made of a non-magnetic material which contains 33 to 80 at % of Ni and one or more kinds of elements selected from Sc, Y, Ti, Zr, Hf, Nb and Ta.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit pursuant to 35 U.S.C. §119(e)(1) of U.S. Provisional Application, No. 60/324,532 filed Sep. 26, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a magnetic recording medium, amethod of manufacture therefor, and a magnetic read/write apparatus thatuses the magnetic recording medium.

[0004] 2. Description of the Related Art

[0005] A magnetic recording medium, that is now commercially available,is exclusively an in-plane magnetic recording medium wherein the axis ofeasy magnetization in a magnetic film is generally oriented parallel tothe substrate.

[0006] In the in-plane magnetic recording medium, there is a possibilitythat the volume of bits becomes too small when the recording density isincreased and magnetic read/write characteristics are deteriorated bythe thermal stability effect. Also medium noise increases under theinfluence of diamagnetism in the boundary of recording bits when therecording density is increased.

[0007] In a so-called perpendicular magnetic recording medium of whichthe axis of easy magnetization in the magnetic film is generallyoriented perpendicular to a substrate, in contrast, recording magneticdomains that have clear boundaries can be formed due to less influenceof diamagnetism in the boundary of recording bits even when therecording density is increased, and therefore noise can be reduced.Moreover, since the recording density can be increased even if thevolume of bits is comparatively large, strong thermal stability effectsare exerted, resulting in much attention to the perpendicular magneticrecording medium. Consequently, a structure of a medium suited for usein perpendicular magnetic recording has been proposed.

[0008] Recently, there has been increasing demand for high-densityrecording in the magnetic recording medium. For this reason, such amagnetic recording medium has been proposed as a layer made of a softmagnetic material, called a soft back layer, is provided between aperpendicular magnetic film that serves as a recording layer and asubstrate so as to improve the efficiency of the flow or the magneticflux between a single pole type head and the magnetic recording medium,in order to use the single pole type head that has high capability ofwriting in the perpendicular magnetic film.

[0009] However, even when the soft back layer is provided, the magneticrecording medium does not have satisfactory performance in theread/write characteristics, thermal stability and the resolution ofrecording, and therefore a magnetic recording medium that is better inthese characteristics has been required.

[0010] Japanese Patent No. 2669529 proposes to enhance lattice matchingproperties between a Ti undercoat film and a Co alloy magnetic film andto improve the orientation of the c axis of the Co alloy magnetic filmby introducing the other element into the Ti undercoat film.

[0011] However, when using a Ti alloy undercoat film, the magneticcluster size in the Co alloy magnetic film increases and the mediumnoise increases, thereby making it difficult to further increase therecording density.

[0012] Japanese Patent Application, First Publication No. Hei 8-180360proposes to improve the orientation of the c axis of the Co alloymagnetic film by using an undercoat film comprising Co and Ru.

[0013] However, the mean crystal grain diameter of the undercoat filmcomprising Co and Ru increases. As a result, the magnetic grain diameterin the Co alloy magnetic film increases and the medium noise increases,thereby making it difficult to further increase the recording density.

[0014] Japanese Patent Application, First Publication No. Sho 63-211117proposes to use a carbon-containing undercoat film.

[0015] However, when using the carbon-containing undercoat film, sincethis film has an amorphous structure, the orientation of the c axis ofthe perpendicular magnetic film deteriorates and the thermal stabilitydeteriorates, thereby making it difficult to further increase therecording density.

[0016] Under the above-described circumstances, the present inventionhas been made, and an object thereof is to provide a magnetic recordingmedium that is capable of recording and read backing information at ahigher density by improving the read/write characteristics and thermalstability, a method of manufacture therefor, and a magnetic read/writeapparatus.

SUMMARY OF THE INVENTION

[0017] To achieve the object described above, the present inventionemployed the following constructions.

[0018] The magnetic recording medium of the present invention ischaracterized in that the orientation control film is made of anon-magnetic material which contains 33 to 80 at % of Ni and one or morekinds of elements selected from Sc, Y, Ti, Zr, Hf, Nb and Ta.

[0019] The orientation control film preferably has an hcp structure.

[0020] The orientation control film can be made of at least one kindselected from the group consisting of NiTa alloy, NiNb alloy, NiTi alloyand NiZr alloy.

[0021] A perpendicular magnetization anisotropy constant Ku of theperpendicular magnetic film is preferably equal to or higher than 1×10⁶erg/cc.

[0022] In the magnetic recording medium of the present invention, it ispreferable that the perpendicular magnetic film have a compositioncontaining CoCrPt as the major constituent and also have a Cr contentequal to or higher than 16 and lower than 24 at % and a Pt content equalto or higher than 14 and lower than 24 at %, and a coercive force (Hc)is equal to or higher than 3000 (Oe), negative nucleation field (−Hn) isequal to or higher than 0 (Oe) and lower than 2500 (Oe), and a ratio ofresidual magnetization (Mr) to saturation magnetization (Ms), Mr/Ms, isequal to or higher than 0.9.

[0023] A mean crystal grain diameter of the orientation control film ispreferably equal to or higher than 2 nm and lower than 20 nm.

[0024] A thickness of the orientation control film is preferably equalto or higher than 0.5 nm and lower than 20 nm.

[0025] It is preferable that the perpendicular magnetization have a Bcontent equal to or higher than 0.1 at % and lower than 5 at % and Δθ50is within a range from 2 to 10°.

[0026] A hard magnetic film made of a hard magnetic material can beprovided between the non-magnetic substrate and the soft magneticundercoat film.

[0027] The method of manufacturing a magnetic recording medium of thepresent invention comprises forming at least a soft magnetic undercoatfilm made of a soft magnetic material, an orientation control film thatcontrols the orientation of a film provided right above, a perpendicularmagnetic film of which the axis of easy magnetization is generallyoriented perpendicular to a substrate, and a protective film, on anon-magnetic substrate, while controlling so that the orientationcontrol film is made of a non-magnetic material which contains 33 to 80at % of Ni and one or more kinds of elements selected from Sc, Y, Ti,Zr, Hf, Nb and Ta.

[0028] The magnetic read/write apparatus of the present inventioncomprises a magnetic recording medium and a magnetic head that recordsinformation on the magnetic recording medium and plays the information,wherein the magnetic recording medium comprises at least a soft magneticundercoat film made of a soft magnetic material, an orientation controlfilm that controls the orientation of a film provided directlythereabove, a perpendicular magnetic film of which the axis of easymagnetization is generally oriented perpendicular to a substrate, and aprotective film, that are provided on a non-magnetic substrate, whilethe orientation control film is made of a non-magnetic material whichcontains 33 to 80 at % of Ni and one or more kinds of elements selectedfrom Sc, Y, Ti, Zr, Hf, Nb and Ta.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a partially sectional view showing the first embodimentof a magnetic recording medium of the present invention.

[0030]FIG. 2 is an electron diffraction image of an orientation controlfilm.

[0031]FIG. 3 is a graph showing an example of a MH curve.

[0032]FIG. 4 is a graph showing another example of a MH curve.

[0033]FIG. 5 is an explanatory view for explaining a method of measuringΔθ50.

[0034]FIG. 6 is an explanatory view for explaining a method of measuringΔθ50.

[0035]FIG. 7 is a graph showing an example of a rocking curve.

[0036]FIG. 8 is a partially sectional view showing the second embodimentof a magnetic recording medium of the present invention.

[0037]FIG. 9 is a partially sectional view showing the third embodimentof a magnetic recording medium of the present invention.

[0038]FIG. 10 is a schematic structural view showing an example of amagnetic read/write apparatus of the present invention; FIG. 10(a) showsthe entire structure, and FIG. 10(b) shows a magnetic head.

DETAILED DESCRIPTION OF THE INVENTION

[0039]FIG. 1 shows the first embodiment of the present invention. Themagnetic recording medium shown here has a structure in which a softmagnetic undercoat film 2, an orientation control film 3, anintermediate film 4, a perpendicular magnetic film 5, a protective film6 and a lubrication film 7 are formed on a non-magnetic substrate 1.

[0040] As the non-magnetic substrate 1, a metallic substrate comprisinga metallic material such as aluminum or aluminum alloy maybe used, and anon-metallic substrate comprising a non-metallic material such as glass,ceramic, silicon, silicon carbide or carbon may be used.

[0041] Examples of the glass substrate include amorphous glass substrateand crystallized glass substrate. As the amorphous glass,general-purpose soda-lime glass, aluminate glass and alumino silicateglass can be used. As the crystallized glass, lithium-based crystallizedglass can be used. As the ceramic substrate, a sintered body containinggeneral-purpose aluminum oxide, aluminum nitride or silicon nitride asthe major constituent, or a fiber-reinforced article thereof can beused.

[0042] As the non-magnetic substrate 1, there can also be usedsubstrates wherein the NiP film is formed on these substrates by aplating method, a sputtering method, or the like.

[0043] The soft magnetic undercoat film 2 is provided in order toincrease the component perpendicular to the substrate of the magneticflux from the magnetic head and to establish more firmly themagnetization of the perpendicular magnetic film 5, that records theinformation, in a direction perpendicular to the substrate 1.

[0044] This action becomes more remarkable when using a single pole typehead for perpendicular recording as a read/write magnetic head.

[0045] The soft magnetic undercoat film 2 is made of a soft magneticmaterial. As the material thereof, a material containing Fe, Ni and Cocan be used.

[0046] Examples of the material of the magnetizing stabilization film 9include FeCo alloys (FeCo, FeCoV and the like), FeNi alloys (FeNi,FeNiMo, FeNiCr, FeNiSi and the like), FeAl alloys (FeAl, FeAlSi,FeAlSiCr, FeAlSiTiRu, FeAlO and the like), FeCr alloys (FeCr, FeCrTi,FeCrCu and the like), FeTa alloys (FeTa, FeTaC, FeTaN and the like),FeMg alloys (FeMgO and the like), FeZr alloys (FeZrN and the like), FeCalloys, FeN alloys, FeSi alloys, FeP alloys, FeNb alloys, FeHf alloys,and FeB alloys.

[0047] There can also be used a material having an Fe content equal toor higher than 60 at % composed of microcrystals comprising FeAlO,FeMgO, FeTaN, FeZrN or the like. In addition, it can also have agranular structure in which the microcrystals are dispersed in a matrix.

[0048] As the material of the soft magnetic undercoat film 2, a Co alloyhaving an amorphous structure, which contains 80 at % or higher of Coand also contains at least one or more of Zr, Nb, Ta, Cr, Mo or thelike, can be used.

[0049] For example, CoZr, CoZrNb, CoZrTa, CoZrCr, and CoZrMo alloys canbe used advantageously as the material.

[0050] The coercive force Hc of the soft magnetic undercoat film 2 ispreferably equal to or lower than 200 (Oe) (preferably equal to or lowerthan 50 (Oe)).

[0051] The coercive force Hc that exceeds the above range is notpreferable by the following reason. That is, soft magneticcharacteristics become insufficient and the read back wave is not aso-called rectangular wave, but a distorted wave.

[0052] The saturation magnetic density Bs of the soft magnetic undercoatfilm 2 is preferably equal to or higher than 0.6 T (preferably equal toor higher than 1 T). Bs that is lower than the above range is notpreferable for the following reason. That is, the read back wave is nota so-called rectangular wave, but a distorted wave.

[0053] Specifically, Bs·t, that is, the product of the saturationmagnetic density Bs of the material that forms the soft magneticundercoat film 2 and the film thickness t of the soft magnetic undercoatfilm 2, is preferably equal to or higher than 40 T·nm (more preferablyequal to or higher than 60 T·nm). A Bs·t that is lower than the aboverange is not preferable for the following reason. That is, the read backwave is sometimes distorted and OW characteristics (over-writecharacteristics) deteriorate.

[0054] It is preferable that the surface of the soft magnetic undercoatfilm 2 (the plane of the orientation control film 3 side) that forms thesoft magnetic undercoat film 2 be partially or completely oxidized.

[0055] Consequently, magnetic fluctuation of the surface of the softmagnetic undercoat film 2 can be suppressed and, therefore, read/writecharacteristics of the magnetic recording medium can be improved byreducing noise caused by the magnetic fluctuation. Also read/writecharacteristics can be improved by refining crystal grains of theorientation control film 3 formed on the soft magnetic undercoat film 2.

[0056] The oxidized portion (oxidized layer) of the surface of the softmagnetic undercoat film 2 can be formed by a method in which the softmagnetic undercoat film 2 is exposed to a gas that includes oxygen afterforming the soft magnetic undercoat film 2, or a method that introducesoxygen into the process gas when forming the portion of the film at thesurface of the soft magnetic undercoat film 2 can be used.

[0057] Specifically, in the case in which the surface of the softmagnetic undercoat film 2 is exposed to an oxygen-containing atmosphere,it may be allowed to stand in oxygen alone, or a gas atmosphere obtainedby diluting oxygen with argon or nitrogen for about 0.3 to 20 seconds.Also the method of exposing the soft magnetic undercoat film 2 toatmospheric air can be employed.

[0058] Particularly, when using a gas obtained by diluting oxygen withargon or nitrogen, stable manufacture can be conducted because itbecomes easy to control the degree of oxidization of the surface of thesoft magnetic undercoat film 2.

[0059] In the case in which oxygen is introduced into a film-forming gasof the soft magnetic undercoat film 2, for example, when using asputtering method as the film-forming method, sputtering may beconducted using a process gas containing oxygen introduced thereinduring only a portion of the film-forming time. As the process gas, forexample, a gas obtained by mixing argon with about 0.05% to 50%(preferably 0.1 to 20%) of oxygen is preferably used.

[0060] The orientation control film 3 is a film provided for controllingthe orientation and crystal grain diameter of the intermediate film 4and the perpendicular magnetic film 5 provided directly thereabove, andis made of a non-magnetic material which contains 33 to 80 at %(preferably 50 to 80 at %) of Ni and one or more kinds of elementsselected from Sc, Y, Ti, Zr, Hf, Nb and Ta.

[0061] The content of one or more kinds selected from Sc, Y, Ti, Zr, Hf,Nb and Ta is preferably set to equal to or higher than 20 at %.

[0062] A Ni content that is lower than 33 at % is not preferable becausethe effect of improving the error rate disappears. On the other hand,the Ni content that exceeds 80 at % is not preferable because theorientation control film 3 is magnetized and medium noise increases.

[0063] The orientation control film 3 is preferably made of at least oneselected from the group consisting of NiTa alloy, NiNb alloy, NiTi alloyand NiZr alloy.

[0064] As the NiTa alloy, an alloy (NiTa) comprising Ni and Ta may beused, and also an alloy, which contains this alloy as the majorconstituent and also contains the other element, can be used.

[0065] As the NiNb alloy, an alloy (NiNb) comprising Ni and Nb may beused, and also an alloy, which contains this alloy as the majorconstituent and also contains the other element, can be used.

[0066] As the NiTi alloy, an alloy (NiTi) comprising Ni and Ti may beused, and also an alloy, which contains this alloy as the majorconstituent and also contains the other element, can be used.

[0067] As the NiZr alloy, an alloy (NiZr) comprising Ni and Zr may beused, and also an alloy, which contains this alloy as the majorconstituent and also contains the other element, can be used.

[0068] The orientation control film 3 preferably has an hcp structure.

[0069] The use of the orientation control film 3 having an hcp structuremakes it possible to improve the orientation of the perpendicularmagnetic film 5 and to improve read/write characteristics and thethermal stability.

[0070] It can be confirmed by examining an electron diffraction imagewhether or not the orientation control film 3 has an hcp structure.

[0071]FIG. 2 shows an electron diffraction image of the orientationcontrol film 3 made of 60Ni-40Ta (which means 60 at % Ni-40% Ta).

[0072] A diffraction image corresponding to hcp-Ni was confirmed by FIG.2 and it is found that the orientation control film 3 has an hcpstructure.

[0073] The thickness of the orientation control film 3 is preferablyequal to or higher than 0.5 nm and lower than 20 nm (more preferablyfrom 1 to 10 nm).

[0074] When the film thickness of the orientation control film 3 iswithin a range from 0.5 to 20 nm (preferably from 1 to 10 nm), theperpendicular orientation of the perpendicular magnetic film 5 becomesparticularly higher and the distance between the magnetic head and thesoft magnetic undercoat film 2 becomes large during read back, andtherefore read/write characteristics can be enhanced withoutdeteriorating the resolution of the read back signal.

[0075] When the thickness falls below the above range, the perpendicularorientation of the perpendicular magnetic film 5 is lowered, andtherefore read/write characteristics and the thermal stabilitydeteriorate.

[0076] Also when the thickness exceeds the range described above, theperpendicular orientation of the perpendicular magnetic film 5 islowered, and therefore read/write characteristics and the thermalstability deteriorate. Since the distance between the magnetic head andthe soft magnetic undercoat film 2 becomes large during read back, theresolution of the read back signal decreases and the noisecharacteristics deteriorate, which is not preferable.

[0077] Since the surface profile of the orientation control film 3exerts an influence on the surface profiles of the perpendicularmagnetic film 5 and protective film 6, the mean surface roughness Ra ofthe orientation control film 3 is preferably set to 2 nm or less inorder to lower the floating height of the magnetic head during recordingand read back by reducing the surface unevenness of the magneticrecording medium.

[0078] Control of the mean surface roughness Ra to 2 nm or less makes itpossible to reduce the surface unevenness of the magnetic recordingmedium, thereby to sufficiently lower the floating height of themagnetic head during recording and read back and to enhance therecording density.

[0079] The orientation control film 3 can contain at least one of oxygenand nitrogen. A method that introduces oxygen or nitrogen into thefilm-forming gas (process gas) when forming the orientation control film3 can be used.

[0080] For example, when using a sputtering method as the film-formingmethod, a gas obtained by mixing argon with about 0.05% to 50%(preferably 0.1 to 20%) of oxygen or a gas obtained by mixing argon withabout 0.01% to 20% (preferably 0.02 to 10%) of nitrogen is preferablyused as the film-forming gas.

[0081] Crystal grains of the orientation control film 3 can be refinedby introducing oxygen or nitrogen.

[0082] When the crystal grain diameter (mean grain diameter) of theorientation control film 3 is too small, the orientation of theperpendicular magnetic film 5 is lowered. On the other hand, when thecrystal grain diameter is too large, crystal grains in the perpendicularmagnetic film 5 become coarse. Therefore, the crystal grain diameter ispreferably equal to or larger than 2 nm and smaller than 20 nm.

[0083] The mean grain diameter can be determined, for example, byobserving crystal grains of the orientation control film 3 by atransmission electron microscope (TEM) and image-processing the imageobserved.

[0084] It is preferable to use, in the intermediate , a material havingan hcp structure. It is preferable to use, in the intermediate, a CoCralloy, a CoCrX₁ alloy or a CoX₁ alloy (X₁: one or more kinds of elementsselected from Pt, Ta, Zr, Ru, Nb, Cu, Re, Ni, Mn, Ge, Si, O, N and B).

[0085] The Co content of the intermediate layer 4 is preferably within arange from 30 to 70 at %.

[0086] The thickness of the intermediate layer 4 is preferably set to 20nm or lower (preferably equal to or lower than 10 nm) in order toprevent deterioration of read/write characteristics due to coarsening ofmagnetic grains in the perpendicular magnetic film 5 and lowering of theresolution of recording due to an increase in distance between themagnetic head and the soft magnetic undercoat film 2.

[0087] Formation of the intermediate layer 4 makes it possible toenhance the perpendicular orientation of the perpendicular magnetic film5, to enhance the coercive force of the perpendicular magnetic film 5,and to further improve the read/write characteristics and the thermalstability.

[0088] The perpendicular magnetic film 5 is a magnetic film, of whichaxis of easy magnetization is generally oriented perpendicular to thesubstrate, and preferably has a composition which contains CoCrPt as themajor constituent and has a Cr content equal to or higher than 16 at %and lower than 24 at % (preferably equal to or higher than 18 at % andlower than 22 at %) and the Pt content equal to or higher than 14 at %and lower than 24 at % (preferably equal to or higher than 15 at % andlower than 20 at %).

[0089] The Cr content of lower than 16 at % is not preferable for thefollowing reason. That is, since exchange coupling between magneticgrains increases, the magnetic cluster size increases and the mediumnoise increases. The Cr content of higher than 24 at % is not preferablefor the following reason. That is, the ratio of residual magnetization(Mr) to saturation magnetization (Ms), Mr/Ms, and the coercive force Hcare lowered.

[0090] The Pt content of lower than 14 at % is not preferable for thefollowing reason. That is, the effect of improving read/writecharacteristics becomes insufficient and the ratio of residualmagnetization (Mr) to saturation magnetization (Ms), Mr/Ms, is loweredand the thermal stability deteriorates. The Pt content of higher than 24at % is not preferable because noise increases.

[0091] As used herein, the major constituent means the constituentincluded in the amount of higher than 50 at %.

[0092] The perpendicular magnetic film 5 preferably has a B contentequal or higher than 0.1 at % and lower than 5 at %, in addition to Co,Cr and Pt. The use of B makes it possible to reduce the magnetic clustersize and to improve read/write characteristics.

[0093] When using a CoCrPt alloy in the perpendicular magnetic film 5,elements can be freely added, in addition to B. Examples of the elementsinclude, but are not limited to, Ta, Mo, Nb, Hf, Ir, Cu and Ru.

[0094] The perpendicular magnetic film 5 can have a single layerstructure made of the CoCrPt material described above, or it can have atwo or multiple layer structure including a layer comprising the CoCrPtalloy material and a layer comprising a material different from theCoCrPt alloy material.

[0095] Also, a perpendicular magnetic film can have a multiple layerstructure in which a Co alloy (CoCr, CoB, Co—SiO₂ or the like) layer anda Pd alloy (PdB, Pd—SiO₂ or the like) layer are laminated, or can have amultiple layer structure including an amorphous material layercomprising TbFeCo and a CoCrPt alloy material layer.

[0096] The thickness of the perpendicular magnetic film 5 is preferablyset within a range from 3 to 60 nm (preferably from 5 to 40 nm) . Whenthe thickness of the perpendicular magnetic film 5 falls below the aboverange, sufficient magnetic flux cannot be obtained and the read backoutput is lowered. The thickness of higher than the above range of theperpendicular magnetic film 5 is not preferable because magnetic grainsin the perpendicular magnetic film 5 become coarse and read/writecharacteristics deteriorate.

[0097] The coercive force Hc of the perpendicular magnetic film 5 is setto 3000 (Oe) or higher. The magnetic recording medium having thecoercive force of lower than 3000 (Oe) is not preferable because it isnot suited to increase the recording density and is also inferior inthermal stability.

[0098] The ratio of residual magnetization (Mr) to saturationmagnetization (Ms), Mr/Ms, of the perpendicular magnetic film 5 ispreferably equal to or higher than 0.9. The magnetic recording mediumhaving Mr/Ms of less than 0.9 is not preferable because it is inferiorin thermal stability.

[0099] The negative nucleation field (−Hn) of the perpendicular magneticfilm 5 is preferably equal to or higher than 0 (Oe) and lower than 2500(Oe). The magnetic recording medium having the negative nucleation field(−Hn) of lower than 0 (Oe) is not preferable because of poor thermalstability.

[0100] The negative nucleation field (−Hn) will now be described.

[0101] As shown in FIG. 3, the negative nucleation field (−Hn) is thenumerical value represented by the distance (Oe) between the point “a”and the point “c” in a MH curve, where the point “a” is a point at whichthe external magnetic field becomes 0 in the process of decreasing theexternal magnetic field from a saturated state of the magnetization, thepoint “b” is a point at which the magnetization becomes 0, and the point“c” is a point of intersection of a tangent which touches the MH curveat the point “a” and a line which shows saturation magnetization.

[0102] Moreover, the negative nucleation field (−Hn) takes a positivevalue in the case in which the point “c” is in a region in which theexternal magnetic field becomes negative (see FIG. 3), and conversely,takes a negative value in the case in which the point “c” is in a regionin which the external magnetic field becomes positive (see FIG. 4).

[0103] A perpendicular magnetization anisotropy constant Ku of theperpendicular magnetic film 5 is preferably equal to or higher than1×10⁶ erg/cc.

[0104] The method of measuring the perpendicular magnetizationanisotropy constant Ku will now be described.

[0105] When a sufficiently large magnetic field is applied to the sampleusing a magnetic torque device, thereby forming a single domain as amagnetic domain of a magnetic film, a rotary power, which allows theaxis of easy magnetization to correspond to the direction of themagnetic field, is applied in the magnetic film.

[0106] Torque T can be represented by Ku·cos4φ, where φ is an anglebetween the direction at which the magnetic field is applied and thedirection of the axis of easy magnetization.

[0107] As described above, torque becomes a periodic function of φ andthe perpendicular magnetization anisotropy constant Ku can be decided byFourier analysis of the curve by which torque is represented.

[0108] In the magnetic recording medium, when the orientation controlfilm 3 is made of a non-magnetic material which contains 33 to 80 at %of Ni and also contains one or more kinds of elements selected from Sc,Y, Ti, Zr, Hf, Nb and Ta, excellent error rate and excellent thermalstability can be obtained.

[0109] This effect is particularly excellent when the perpendicularmagnetization anisotropy constant Ku of the perpendicular magnetic film5 is equal to or higher than 1×10⁶ erg/cc.

[0110] Table 1 shows characteristics of the case where NiTa, Ti or C isused in the orientation control film 3 and the perpendicularmagnetization anisotropy constant Ku is set within a range from 0.7×10⁶to0.9×10⁶erg/cc (Examples 1 to 3) and characteristics of the case wherethe perpendicular magnetization anisotropy constant Ku is set within arange from 1.5×10⁶ to 1.8×10⁶ erg/cc (Examples 4 to 6). TABLE 1ORIENTATION CONTROL MAGNETIC FILM ERROR RATE THERMAL STABILITY KuUNDERCOAT FILM (at %) (10^(X)) (%/DECADE) (erg/cc) EXAMPLE 1 NiTa66Co-20Cr-12Pt-2B −5.1 −1.8 0.9 × 10⁶ EXAMPLE 2 Ti 66Co-20Cr-12Pt-2B−3.8 −2.5 0.8 × 10⁶ EXAMPLE 3 C 66Co-20Cr-12Pt-2B −4.2 −2.9 0.7 × 10⁶EXAMPLE 4 NiTa 61Co-20Cr-17Pt-2B −5.6 −0.5 1.7 × 10⁶ EXAMPLE 5 Ti61Co-20Cr-17Pt-2B −3.2 −0.4 1.8 × 10⁶ EXAMPLE 6 C 61Co-20Cr-17Pt-2B −3.5−1.8 1.5 × 10⁶

[0111] As is apparent from Table 1, as compared with the case of usingTi or C in the orientation control film 3 (Examples 2, 3, 5 and 6), theread/write characteristics (error rate) and the thermal stability wereimproved when using NiTa in the orientation control film 3 (Examples 1and 4).

[0112] As is apparent from a comparison in this improving effect betweenthe medium having small Ku of the perpendicular magnetic film 5(Examples 1 to 3) and the medium having large Ku (Examples 4 to 6), alarger improving effect could be obtained in the case where Ku is large(Example 4).

[0113] As is apparent from this fact, the effect of improving magneticcharacteristics obtained by using NiTa in the orientation control film 3becomes more superior as Ku becomes larger.

[0114] Δθ50 of the perpendicular magnetic film 5 is preferably within arange from 2 to 10°.

[0115] Δθ50 of lower than 2° is not preferable because exchange couplingbetween magnetic grains increases and read/write characteristicsdeteriorate. Δθ50 of higher than 10° is not preferable because the ofresidual magnetization (Mr) to saturation magnetization (Ms), Mr/Ms,deteriorates and the thermal stability deteriorates.

[0116] As used herein, the term “Δθ50” means inclined distribution ofthe film and specifically refers to a half-value of a peak of a rockingcurve relating to the specific orientation plane on the surface of thefilm. The smaller the numerical value of Δθ50, the higher the crystalorientation of the film.

[0117] An example of the method of measuring Δθ50 will now be described.

[0118] (1) Determination of Peak Position

[0119] As shown in FIG. 5, a disk D, in which a perpendicular magneticfilm 5 has been formed in the surface side, is irradiated with anincident X-ray 21 and a diffraction X-ray 22 is detected by adiffraction X-ray detector 23.

[0120] The position of the detector 23 is set so that the angle of thediffraction X-ray 22 detected by the detector 23 to the incident X-ray21 (the angle of the diffraction X-ray 22 to an extension line 24 of theincident X-ray 21) becomes two times larger than an incident angle θ ofthe incident X-ray 21 to the surface of the disk D, that is, 2θ.

[0121] The intensity of the diffraction X-ray 22 is measured by thedetector 23 using a θ-2θ scanning method wherein, during the irradiationwith the incident X-ray 21, the incident angle θ of the incident X-ray21 is changed by changing the direction of the disk D and, at the sametime, the position of the detector 23 is charged while maintaining theangle of the diffraction X-ray 22 to the incident X-ray 21 at 2θ (theangle that is two times larger than the incident angle θ of the incidentX-ray 21).

[0122] Consequently, a relationship between θ and the intensity of thediffraction X-ray 22 is examined, thereby to determine the position ofthe detector 23, where the intensity of the diffraction X-ray 22 becomesmaximum. The angle 2θ of the diffraction X-ray 22 at this position ofthe detector to the incident X-ray 21 refers to 2θp.

[0123] The crystal plane, that is dominant in the film, can bedetermined from the resulting angle 2θp.

[0124] (2) Determination of Rocking Curve

[0125] As shown in FIG. 6, the incident angle θ of the incident X-ray 21is changed by changing the direction of the disk D in the state that thedetector 23 is fixed to the position where the angle 2θ of thediffraction X-ray 22 became 2θp, thereby to make a rocking curve showinga relationship between the incident angle θ and the intensity of thediffraction X-ray 22 detected by the detector 23.

[0126] Since the position of the detector 23 is fixed to the positionwhere the angle 2θ of the diffraction X-ray 22 became 2θp, the rockingcurve shows the distribution of gradient of the crystal plane of thesurface of the film to the plane of the disk D.

[0127]FIG. 7 is a graph showing an example of the rocking curve. Theterm “Δθ50” refers to a half-value width of a peak that shows theorientation plane in this rocking curve.

[0128] In the perpendicular magnetic film 5, the mean grain diameter ofcrystal grains is preferably within a range from 5 to 15 nm.

[0129] The mean grain diameter can be determined, for example, byobserving crystal grains of the perpendicular magnetic film 5 by atransmission electron microscope (TEM) and image-processing the imageobserved.

[0130] The protective film 6 is for preventing corrosion of theperpendicular magnetic film 5, and at the same time, prevents damage tothe medium surface when the magnetic head comes into contact with themedium. Conventionally well-known materials can be used and, forexample, a material containing C, SiO₂, or ZrO₂ can be used.

[0131] The thickness of the protective film 6 is preferably within arange from 1 to 10 nm.

[0132] It is preferable to use, as a lubricant 7, perfluoropolyether,fluorinated alcohol, fluorinated carboxylic acid, or the like.

[0133] In the magnetic recording medium with the above construction,since the orientation control film 3 is made of a non-magnetic materialwhich contains 33 to 80 at % of Ni and also contains one or more kindsof elements selected from Sc, Y, Ti, Zr, Hf, Nb and Ta, the coerciveforce Hc is enhanced and Mr/Ms is improved, thereby making it possibleto increase the negative nucleation field (−Hn).

[0134] Therefore, excellent thermal stability can be obtained.Furthermore, read/write characteristics can be improved.

[0135] The thermal stability refers to a phenomenon wherein recordingbits become unstable and thermal missing of recorded data occurs. In themagnetic recording medium apparatus, it appears as damping over elapseof time of the read back output of recorded data.

[0136] In the present invention, when the perpendicular magnetic filmhas a multiple layer structure composed of plural layers, at least oneof these layers may be provided with the construction of theperpendicular magnetic film 5 in the first embodiment described above.

[0137]FIG. 8 shows the second embodiment of the magnetic recordingmedium of the present invention. In this magnetic recording medium, ahard magnetic film 8 made of a hard magnetic material is providedbetween a non-magnetic substrate 1 and a soft magnetic undercoat film 2.

[0138] It is preferable to use, in the hard magnetic film 8, a CoSmalloy or a CoCrPtX₂ alloy (X₂: one or more kinds of elements selectedfrom Pt, Ta, Zr, Nb, Cu, Re, Ni, Mn, Ge, Si, O, N and B).

[0139] The coercive force Hc of the hard magnetic film 8 is preferablyequal to or higher than 500 (Oe) (preferably equal to or higher than1000 (Oe)).

[0140] The thickness of the hard magnetic film 8 is preferably equal toor lower than 150 nm (preferably equal to or lower than 70 nm). Athickness of more than 150 nm of the hard magnetic film 8 is notpreferable because the mean surface roughness Ra of the orientationcontrol film 3 becomes larger.

[0141] The hard magnetic film 8 is preferably provided with such aconstruction that exchange coupling between the hard magnetic film andthe soft magnetic undercoat film 2 is formed and the magnetic film ismagnetized in the radial direction of the substrate.

[0142] By providing the hard magnetic film 8, formation of extremelylarge magnetic domains in the soft magnetic undercoat film 2 can besuppressed more effectively, and therefore the occurrence of spike noisedue to magnetic domains can be prevented and the error rate duringrecording and read back can be sufficiently lowered.

[0143] To enhance the orientation of the hard magnetic film 8, anundercoat film made of a Cr alloy or a B2 structural material may beformed between anon-magnetic substrate 1 and a hard magnetic film 8.

[0144]FIG. 9 shows the third embodiment of the magnetic recording mediumof the present invention. In this magnetic recording medium, amagnetizing stabilization film 9 made of a soft magnetic material isprovided between a perpendicular magnetic film 5 and a protective film6.

[0145] Examples of the material of the magnetizing stabilization film 9include FeCo alloys (FeCo, FeCoV and the like), FeNi alloys (FeNi,FeNiMo, FeNiCr, FeNiSi and the like), FeAl alloys (FeAl, FeAlSi,FeAlSiCr, FeAlSiTiRu, FeAlO and the like), FeCr alloys (FeCr, FeCrTi,FeCrCu and the like), FeTa alloys (FeTa, FeTaC, FeTaN and the like),FeMg alloys (FeMgO and the like), FeZr alloys (FeZrN and the like), FeCalloys, FeN alloys, FeSi alloys, FeP alloys, FeNb alloys, FeHf alloys,and FeB alloys.

[0146] There can also be used a material having an Fe content equal toor higher than 60 at % composed of microcrystals comprising FeAlO,FeMgO, FeTaN, FeZrN or the like. In addition, it can also have agranular structure in which the microcrystals are dispersed in a matrix.

[0147] As the material of the magnetizing stabilization film 9, a Coalloy having an amorphous structure, which contains 80 at % or higher ofCo and also contains at least one or more of Zr, Nb, Ta, Cr, Mo or thelike, can be used.

[0148] For example, CoZr, CoZrNb, CoZrTa, CoZrCr, and CoZrMo alloys canbe used advantageously as the material.

[0149] The coercive force Hc of the magnetizing stabilization film 9 ispreferably equal to or lower than 200 (Oe) (preferably equal to or lowerthan 50 (Oe)).

[0150] The saturation magnetic density Bs of the magnetizingstabilization film 9 is preferably equal to or higher than 0.4 T(preferably equal to or higher than 1 T).

[0151] Bs·t, that is the product of the saturation magnetic density Bsof the material and the film thickness t of the magnetizingstabilization film 9, is preferably equal to or higher than 7.2 T·nm.Bs·t that exceeds the above range is not preferable because the readback output is lowered.

[0152] By providing a magnetizing stabilization film 9 made of a softmagnetic film between a perpendicular magnetic film 5 and a protectivefilm 6, an improvement in thermal stability and an increase in read backoutput can be achieved.

[0153] This reason is believed to be as follows. That is, thefluctuation of the magnetization in the surface of the perpendicularmagnetic film 5 is stabilized by the magnetizing stabilization film 9,so that leakage flux is not influenced by this fluctuation and the readback output increases. In addition, by providing the magnetizingstabilization film 9, the magnetization of the perpendicular magneticfilm 5 in the perpendicular direction and the magnetization of the softmagnetic undercoat film 2 and the magnetizing stabilization film 9 inthe in-plane direction form a closed circuit. Due to this action,excellent thermal stability is obtained because the magnetization of theperpendicular magnetic film 4 is established more strongly in theperpendicular direction.

[0154] In the manufacture of the magnetic recording medium having theconstruction described above, a soft magnetic undercoat film 2, anorientation control film 3, an intermediate film 4 and a perpendicularmagnetic film 5 are formed in sequence on a substrate 1 by a sputteringmethod, vacuum deposition, ion plating or the like.

[0155] An oxidizing treatment can be carried out on the surface of thesoft magnetic undercoat film 2, if necessary.

[0156] In the formation of the orientation control film 3, anon-magnetic material, which contains 33 to 80 at % of Ni and alsocontains one or more kinds of elements selected from Sc, Y, Ti, Zr, Hf,Nb and Ta, is used.

[0157] The orientation control film 3 can contain at least one of oxygenand nitrogen. A method that introduces oxygen or nitrogen into thefilm-forming gas (process gas) when forming the orientation control film3 can be used.

[0158] In the formation of the perpendicular magnetic film 5, thematerial and film-forming conditions are preferably selected so that theperpendicular magnetization anisotropy constant Ku becomes 1×10⁶ erg/ccor higher.

[0159] In the formation of the perpendicular magnetic film 5, thematerial and film-forming conditions are preferably selected so that“Δθ50” is set within range from 2 to 10°.

[0160] Next, the protective film 6 is preferably formed by a plasma CVDmethod, an ion beam method, a sputtering method or the like.

[0161] To form a lubricant 7, conventionally well-known methods such asdip coating method and spin coating method can be employed.

[0162] In the manufacture of the magnetic recording medium shown in FIG.8, a hard magnetic film 8 is formed between a substrate 1 and a softmagnetic undercoat film 2 by a sputtering method. In the manufacture ofthe magnetic recording medium shown in FIG. 9, a magnetizingstabilization film 9 is formed between a perpendicular magnetic film 5and a protective film 6 by a sputtering method.

[0163]FIG. 10 is a sectional structural view showing an example of themagnetic read/write apparatus according to the present invention. Themagnetic read/write apparatus shown in this drawing comprises a magneticrecording medium 10 having the construction described above, a mediumdrive unit 11 that rotates this magnetic recording medium 10, a magnetichead 12 that carries out recording and read back of the information onthe magnetic recording medium 10, a head drive unit 13 that drives themagnetic head 12, and a read/write signal processing system 14. The readback signal processing system 14 sends a recorded signal to the magnetichead 12 after processing the input data, and outputs the data afterprocessing the read back signal from the magnetic head 12.

[0164] Examples of the magnetic head 12 include a single pole type headfor perpendicular recording.

[0165] As shown in FIG. 10(b), as the single pole type head, a singlepole type head with a construction comprising a main magnetic pole 12 a,an auxiliary magnetic pole 12 b and a coil 12 d provided at a connectionunit 12 c that connects these magnetic poles can be preferably used.

[0166] According to the magnetic read/write apparatus described above,since the magnetic recording medium 10 is used, the thermal stabilityand read/write characteristics can be enhanced.

[0167] Therefore, it is made possible to prevent problems such as datamissing and to increase high recording density.

EXAMPLES

[0168] The operational effect of the present invention will now beclarified by way of examples. However, the present invention is notlimited to the following examples.

Example 1

[0169] A washed glass substrate 1 (Ohara Co.; diameter: 2.5 inches) wasaccommodated in the film formation chamber of a DC magnetron sputteringapparatus (ANELVA, C-3010), and after expelling air in the filmformation chamber up to an ultimate vacuum of 1×10⁻⁵ Pa, a soft magneticundercoat film 2 (thickness: 100 nm) was formed on the glass substrate 1using a target comprising 89Co-4Zr-7Nb (Co content: 89 at %, Zr content:4 at %, Nb content: 7 at %) at a substrate temperature of 100° C. orlower. Using a vibrating sample magnetometer (VSM), it was confirmedthat Bs·t (T·nm), that is the product of the saturation magnetic densityBs (T) of this film and the film thickness t (nm), is 110 (T·nm).

[0170] After heating the substrate to 200° C., an orientation controlfilm 3 having a thickness of 8 nm was formed on the soft magneticundercoat film 2 using a 60Ni-40Ta target and an intermediate layer 4having a thickness of 5 nm was formed thereon using a 65Co-30Cr-5Btarget, and then a perpendicular magnetic film 5 having a thickness of25 nm was formed thereon using a 61Co-20Cr-17Pt-2B target. In thesputtering step, a film was formed under a pressure of 0.5 Pa usingargon as a process gas for forming a film.

[0171] Next, a protective film 6 having a thickness of 5 nm was formedby a CVD method.

[0172] Next, a lubrication film 7 made of perfluoropolyether was formedby a dip coating method to obtain a magnetic recording medium (see Table2).

[0173] To confirm the crystal structure of the orientation control film3, a soft magnetic undercoat film 2 (89Co-4Zr-7Nb) was formed on thesubstrate 1 and an orientation control film 3 (thickness: 8 nm) made of60Ni-40Ta was formed thereon, and then the electron diffraction image ofthe orientation control film 3 was examined. As a result, it has beenfound that the crystal of the orientation control film 3 has an hcpstructure.

Examples 2 to 13

[0174] In the same manner as in Example 1, except that the compositionor thickness of the orientation control film 3 was changed, magneticrecording media were manufactured (see Table 2)

Comparative Examples 1 to 3

[0175] In the same manner as in Example 1, except that the orientationcontrol film 3 was formed using a target made of Ti, 60Ru-40Co or C,magnetic recording media were manufactured (see Table 2).

Comparative Examples 4 and 5

[0176] In the same manner as in Example 1, except that the orientationcontrol film 3 was formed using a target made of 85Ni-15Ta or 25Ni-75Ta,magnetic recording media were manufactured (see Table 2).

[0177] With respect to magnetic recording media of these Examples andComparative Example, read/write characteristics and magnetostaticcharacteristics were evaluated. The evaluation was conducted using aread write analyzer RWA1632 manufactured by GUZIK Co. and a spin standS1701MP.

[0178] In the evaluation of magnetic characteristics, the measurementwas conducted at a recording frequency of 520 kFCI using a magnetic headwherein a single magnetic pole head is used at the writing portion and aGMR element is used at the read back portion.

[0179] The evaluation of the thermal stability was made by calculatingthe decrease rate (%/decade) of the output of the read back output afterwriting at a track recording density of 50 kFCI under the conditions of70° C. one second after writing based on (So−S)×100/(So×3). In thisequation, So denotes the read back output when one second has passedafter the signal recording onto the magnetic recording medium, and Sdenotes the read back output after 1000 seconds.

[0180] The dispersion degree of the c axis of the perpendicular magneticfilm 5 was calculated from the rocking curve. It is expressed by ahalf-value width (Δθ50) of a maximum intensity. These test results areshown in Table 2. TABLE 2 SOFT MAGNETIC UNDERCOAT FILM ORIENTATIONCONTROL FILM Bs · T COMPOSITION THICKNESS INTERMEDIATE PERPENDICULARCOMPOSITION (T · nm) (at %) (nm) FILM MAGNETIC FILM EXAMPLE 1 CoZrNb 11060Ni-40Ta 8 *1 *2 EXAMPLE 2 CoZrNb 110 60Ni-40Hf 8 *1 *2 EXAMPLE 3CoZrNb 110 55Ni-45Nb 8 *1 *2 EXAMPLE 4 CoZrNb 110 50Ni-50Y 8 *1 *2EXAMPLE 5 CoZrNb 110 75Ni-25Zr 8 *1 *2 EXAMPLE 6 CoZrNb 110 65Ni-35Ti 8*1 *2 EXAMPLE 7 CoZrNb 110 60Ni-30Nb-10Ta 8 *1 *2 EXAMPLE 8 CoZrNb 11035Ni-33Y-32Zr 8 *1 *2 EXAMPLE 9 CoZrNb 110 60Ni-30Hf-10Cr 8 *1 *2EXAMPLE 10 CoZrNb 110 65Ni-30Ta-5Zr 8 *1 *2 EXAMPLE 11 CoZrNb 11060Ni-40Ta 0.5 *1 *2 EXAMPLE 12 CoZrNb 110 60Ni-40Ta 18 *1 *2 EXAMPLE 13CoZrNb 110 60Ni-40Ta 40 *1 *2 COMPARATIVE EXAMPLE 1 CoZrNb 110 Ti 20 *1*2 COMPARATIVE EXAMPLE 2 CcZrNb 110 60Ru-40Co 30 *1 *2 COMPARATIVEEXAMPLE 3 CoZrNb 110 C 10 *1 *2 COMPARATIVE EXAMPLE 4 CoZrNb 11085Ni-15Ta 8 *1 *2 COMPARATIVE EXAMPLE 5 CoZrNb 110 25Ni-75Ta 8 *1 *2READ/WRITE PERPENDICULAR CHARCTERISTICS THERMAL MAGNETIC ERROR RATESTABILITY MAGNETOSTATIC CHARATERISTICS FILM (10^(X)) (%/DECADE) Hc (Oe)Mr/Ms −Hn (Oe) Ku (erg/cc) Δ θ 50 (°) EXAMPLE 1 −5.6 −0.5 4064 0.96 7361.7 × 10⁶ 6.1 EXAMPLE 2 −5.3 −0.7 3328 0.93 526 1.7 × 10⁶ 5.8 EXAMPLE 3−5.4 −0.5 3607 0.93 430 1.8 × 10⁶ 6.1 EXAMPLE 4 −5.1 −0.6 3934 0.96 5561.6 × 10⁶ 6.8 EXAMPLE 5 −5.7 −0.5 3791 0.95 708 1.7 × 10⁶ 5.7 EXAMPLE 6−5.2 −0.7 3503 0.94 644 1.7 × 10⁶ 6.0 EXAMPLE 7 −5.9 −0.4 4241 0.93 7211.9 × 10⁶ 5.2 EXAMPLE 8 −5.5 −0.6 4047 0.93 532 1.7 × 10⁶ 6.7 EXAMPLE 9−6.0 −0.6 3646 0.95 624 1.8 × 10⁶ 6.1 EXAMPLE 10 −5.9 −0.4 4187 0.97 7971.6 × 10⁶ 5.3 EXAMPLE 11 −5.5 −0.6 3590 0.97 579 1.7 × 10⁶ 6.8 EXAMPLE12 −5.5 −0.9 3576 0.91 230 1.6 × 10⁶ 6.6 EXAMPLE 13 −5.3 −1.2 3552 0.90140 1.8 × 10⁶ 8.1 COMPARATIVE EXAMPLE 1 −3.2 −0.4 3180 0.99 1020  1.8 ×10⁶ 4.8 COMPARATIVE EXAMPLE 2 −4.2 −0.6 3950 0.92 260 1.7 × 10⁶ 6.9COMPARATIVE EXAMPLE 3 −3.5 −1.8 3300 0.86 — 1.5 × 10⁶ 12.8  COMPARATIVEEXAMPLE 4 −3.8 −0.4 3990 0.94 916 1.7 × 10⁶ 6.2 COMPARATIVE EXAMPLE 5−3.5 −1.2 3552 0.91 331 1.7 × 10⁶ 8.9

[0181] As is apparent from Table 2, Examples using a non-magneticmaterial, which contains 33 to 80 at % of Ni and also contains 20 at %or higher of one or more kinds of elements selected from Sc, Y, Ti, Zr,Hf, Nb and Ta in the orientation control film 3 exhibit excellentread/write characteristics as compared with Comparative Examples.

Examples 14 to 22

[0182] In the same manner as in Example 1, except for selecting theconditions the perpendicular magnetic film 5 as shown in Table 3,magnetic recording media were manufactured (see Table 3).

[0183] With respect to magnetic recording media of these Examples andComparative Examples, the evaluation test was conducted. The results areshown in Table 3. TABLE 3 SOFT MAGNETIC UNDERCOAT FILM PERPENDICULARMAGNETIC FILM COMPOSITION Bs · t ORIENTATION INTERMEDIATE COMPOSITIONTHICKNESS (at %) (T · nm) CONTROL FILM FILM (at %) (nm) EXAMPLE 1 CoZrNb110 *1 *2 61Co-20Cr-17Pt-2B 25 EXAMPLE 14 CoZrNb 110 *1 *264Co-17Cr-17Pt 25 EXAMPLE 15 CoZrNb 110 *1 *2 58Co-24Cr-17Pt 25 EXAMPLE16 CoZrNb 110 *1 *2 65Co-20Cr-14Pt 25 EXAMPLE 17 CoZrNb 110 *1 *257Co-20Cr-23Pt 25 EXAMPLE 18 CoZrNb 110 *1 *2 61Co-20Cr-17Pt-1Ir 25EXAMPLE 19 CoZrNb 110 *1 *2 61Co-20Cr-17Pt-2Cu 25 EXAMPLE 20 CoZrNb 110*1 *2 61Co-20Cr-13Pt 25 EXAMPLE 21 CoZrNb 110 *1 *2 55Co-20Cr-25Pt 25EXAMPLE 22 CoZrNb 110 *1 *2 56Co-25Cr-17Pt 25 READ/WRITE CHARACTERISTICSTHERMAL ERROR RATE STABILITY MAGNETOSTATIC CHARACTERISTICS (10^(X))(%/DECADE) Hc (Oe) Mr/Ms −Hn (Oe) Ku (erg/cc) EXAMPLE 1 −5.6 −0.5 40640.96 736 1.7 × 10⁶ EXAMPLE 14 −5.0 −0.3 4049 0.98 1488  2.7 × 10⁶EXAMPLE 15 −5.4 −1.1 3369 0.91 108 1.2 × 10⁶ EXAMPLE 16 −5.1 −0.9 36100.91 233 1.1 × 10⁶ EXAMPLE 17 −5.0 −0.8 3511 0.92 330 1.5 × 10⁶ EXAMPLE18 −5.5 −0.4 3557 0.96 537 2.1 × 10⁶ EXAMPLE 19 −5.4 −0.3 4421 0.991040  2.1 × 10⁶ EXAMPLE 20 −4.4 −1.8 3699 0.83 — 0.9 × 10⁶ EXAMPLE 21−4.1 −0.8 2961 0.87 — 0.9 × 10⁶ EXAMPLE 22 −5.4 −2.9 2880 0.76 — 0.8 ×10⁶

[0184] As is apparent from Table 3, magnetic recording media wherein theCr content is equal to or higher than 16 at % and lower than 24 at % andthe Pt content is equal to or higher than 14 at % and lower than 24 at %exhibit excellent magnetic characteristics as compared with Exampleswherein the Cr content and the Pt content deviate from the above range.

[0185] It is also apparent that Examples wherein the coercive force (Hc)is equal to or higher than 3000 (Oe) and the negative nucleation field(−Hn) is equal to or higher than 0 (Oe) and lower than 2500 (Oe) and,moreover, Mr/Ms is equal to or higher than 0.9 exhibit excellentmagnetic characteristics as compared with Comparative Examples 4 and 5.

Examples 23 to 29

[0186] In the same manner as in Example 1, except for selecting thecomposition of the soft magnetic undercoat film 2 as shown in Table 4,magnetic recording media were manufactured (see Table 4).

[0187] With respect to magnetic recording media of these Examples, theevaluation test was conducted. The results are shown in Table 4. TABLE 4SOFT MAGNETIC ORIENTATION CONTROL UNDERCOAT FILM FILM INTERMEDIATE FILMCOMPOSITION Bs · t COMPOSITION THICKNESS COMPOSITION THICKNESS (at %) (T· nm) (at %) (nm) (at %) (nm) EXAMPLE 1 CoZrNb 110 60Ni-40Ta 865Co-30Cr-5B 5 EXAMPLE 23 CoTaZr 110 60Ni-40Ta 8 65Co-30Cr-5B 5 EXAMPLE24 FeAlSi 110 60Ni-40Ta 8 65Co-30Cr-5B 5 EXAMPLE 25 FeTaC 110 60Ni-40Ta8 65Co-30Cr-5B 5 EXAMPLE 26 FeAlO 110 60Ni-40Ta 8 65Co-30Cr-5B 5 EXAMPLE27 CoZrNb  5 60Ni-40Ta 8 65Co-30Cr-5B 5 EXAMPLE 28 CoZrNb  20 60Ni-40Ta8 65Co-30Cr-5B 5 EXAMPLE 29 CoZrNb 400 60Ni-40Ta 8 65Co-30Cr-5B 5READ/WRITE CHARACTERISTICS THERMAL MAGNETOSTATIC PERPENDICULAR ERRORRATE STABILITY CHARACTERISTICS MAGNETIC FILM (10^(X)) (%/DECADE) Hc (Oe)Mr/Ms −Hn (Oe) EXAMPLE 1 *1 −5.6 −0.5 4064 0.96 736 EXAMPLE 23 *1 −5.5−0.6 3989 0.98 669 EXAMPLE 24 *1 −5.3 −0.6 4011 0.95 609 EXAMPLE 25 *1−5.7 −0.5 3859 0.95 790 EXAMPLE 26 *1 −5.8 −0.7 3992 0.95 660 EXAMPLE 27*1 −5.3 −0.6 4009 0.97 590 EXAMPLE 28 *1 −5.5 −0.5 3955 0.97 692 EXAMPLE29 *1 −5.6 −0.6 4102 0.96 701

[0188] As is apparent from Table 4, in all Examples, excellentread/write characteristics could be obtained.

Examples 30 to 32

[0189] In the same manner as in Example 1, except that the soft magneticundercoat film 2 was oxidized by exposing the surface thereof to anoxygen-containing gas (pure oxygen (100% O₂), 50% O₂-50% Ar, or air),magnetic recording media was manufactured (see Table 5).

[0190] With respect to magnetic recording media of these Examples, theevaluation test was conducted. The results are shown in Table 5. TABLE 5SOFT MAGNETIC UNDERCOAT FILM INTERMEDIATE FILM COMPOSITION Bs · tEXPOSURE OXIDIZED COMPOSITION THICKNESS INTERMEDIATE (at %) (T · nm) GASLAYER (nm) (at %) (nm) FILM EXAMPLE 1 CoZrNb 110 — — 60Ni-40Ta 8 *1EXAMPLE 30 CoZrNb 110 100% O₂ 2 60Ni-40Ta 8 *1 EXAMPLE 31 CoZrNb 110 50%O₂-50% 1 60Ni-40Ta 8 *1 Ar EXAMPLE 32 CoZrNb 110 Air 2 60Ni-40Ta 8 *1READ/WRITE CHARACTERISTICS THERMAL PERPENDICULAR ERROR RATE STABILITYORIENTATION CONTROL FILM MAGNETIC FILM (10^(X)) (%/DECADE) Hc (Oe) Mr/Ms−Hn (Oe) EXAMPLE 1 *2 −5.6 −0.5 4064 0.96 736 EXAMPLE 30 *2 −5.9 −0.64103 0.98 689 EXAMPLE 31 *2 −5.8 −0.6 3908 0.96 801 EXAMPLE 32 *2 −5.8−0.5 3899 0.99 778

[0191] As is apparent from Table 5, excellent read/write characteristicscould be obtained by oxidizing the soft magnetic undercoat film 2.

Examples 33 to 39

[0192] In the same manner as in Example 1, except for electing thematerial and the thickness of the intermediate film 4 as shown in Table6, magnetic recording media were manufactured (see Table 6).

[0193] With respect to magnetic recording media of these Examples, theevaluation test was conducted. The results are shown in Table 6. TABLE 6SOFT MAGNETIC ORIENTATION CONTROL UNDERCOAT FILM FILM INTERMEDIATE FILMCOMPOSITION Bs · T COMPOSITION THICKNESS COMPOSITION THICKNESS (at %) (T· nm) (at %) (nm) (at %) (nm) EXAMPLE 1 CoZrNb 110 60Ni-40Ta 865Co-30Cr-5B 5 EXAMPLE 33 CoZrNb 110 60Ni-40Ta 8 65Co-30Cr-5Pt 5 EXAMPLE34 CoZrNb 110 60Ni-40Ta 8 54Co-28Cr-10Pt-8B 5 EXAMPLE 35 CoZrNb 11060Ni-40Ta 8 60Co-40Ru 5 EXAMPLE 36 CoZrNb 110 60Ni-40Ta 8 55Co-45B 5EXAMPLE 37 CoZrNb 110 60Ni-40Ta 8 — — EXAMPLE 38 CoZrNb 110 60Ni-40Ta 865Co-30Cr-5B 15  EXAMPLE 39 CoZrNb 110 60Ni-40Ta 8 65Co-30Cr-5B 40 READ/WRITE CHARACTERISTICS THERMAL MAGNETOSTATIC PERPENDICULAR ERRORRATE STABILITY CHARACTERISTICS MAGNETIC FILM (10^(X)) (%/DECADE) Hc (Oe)Mr/Ms −Hn (Oe) EXAMPLE 1 *1 −5.6 −0.5 4064 0.96  736 EXAMPLE 33 *1 −5.4−0.6 4030 0.97 1020 EXAMPLE 34 *1 −5.9 −0.6 4021 0.95 1100 EXAMPLE 35 *1−5.6 −0.5 3991 0.96 1210 EXAMPLE 36 *1 −5.8 −0.6 4288 0.93 1260 EXAMPLE37 *1 −5.2 −0.9 4010 0.94  660 EXAMPLE 38 *1 −5.2 −0.4 4515 0.97 1350EXAMPLE 39 *1 −4.6 −0.4 4377 0.98 1300

[0194] As is apparent from Table 6, in all Examples, excellentread/write characteristics could be obtained.

Examples 40 to 42

[0195] In the same manner as in Example 1, except that an undercoat film(thickness: 20 nm) made of 94Cr-6Mo was provided between thenon-magnetic substrate 1 and the soft magnetic undercoat film 2 and ahard magnetic film 8 shown in Table 7 was provided thereon, magneticrecording media were manufactured (see Table 7).

[0196] With respect to magnetic recording media of these Examples, theevaluation test was conducted. The results are shown in Table 7. TABLE 7SOFT MAGNETIC ORIENTATION CONTROL HARD MAGNETIC FILM UNDERCOAT FILM FILMCOMPOSITION THICKNESS COMPOSITION Bs · T COMPOSITION THICKNESSINTERMEDIATE (at %) (nm) (at %) (T · nm) (at %) (nm) FILM EXAMPLE 1 — —CoZrNb 110 60Ni-40Ta 8 *1 EXAMPLE 40 64Co-20Cr-14Pt-2B 50 CoZrNb 11060Ni-40Ta 8 *1 EXAMPLE 41 64Co-20Cr-14Pt-2B 150  CoZrNb 110 60Ni-40Ta 8*1 EXAMPLE 42 84Co-16Sm 50 CoZrNb 110 60Ni-40Ta 8 *1 READ/WRITEPERPENDICULAR CHARACTERISTICS THERMAL MAGNETOSTATIC MAGNETIC ERROR RATESTABILITY CHARACTERISTICS SPIKE FILM (10^(X)) (%/DECADE) Hc (Oe) Mr/Ms−Hn (Oe) NOISE EXAMPLE 1 *2 −5.6 −0.5 4064 0.96 736 *3 EXAMPLE 40 *2−5.5 −0.6 4009 0.97 810 NONE EXAMPLE 41 *2 −5.5 −0.5 4103 0.95 699 NONEEXAMPLE 42 *2 −5.3 −0.6 3990 0.96 703 NONE

[0197] As is apparent from Table 7, spike-like noise caused by amagnetic wall in the soft magnetic undercoat film 2 could be suppressedwithout deteriorating the read/write characteristics.

[0198] As described above, the magnetic recording medium of the presentinvention comprises at least a soft magnetic undercoat film made of asoft magnetic material, an orientation control film that controls theorientation of a film provided right above, a perpendicular magneticfilm, of which axis of easy magnetization is generally orientedperpendicular to a substrate, and a protective film, that are providedon a non-magnetic substrate, wherein the orientation control film ismade of a non-magnetic material which contains 33 to 80 at % of Ni andone or more kinds of elements selected from Sc, Y, Ti, Zr, Hf, Nb andTa. Therefore, read/write characteristics and thermal stability can beimproved.

1. A magnetic recording medium comprising at least a soft magneticundercoat film made of a soft magnetic material, an orientation controlfilm that controls the orientation of a film provided directlythereabove, a perpendicular magnetic film, of which the axis of easymagnetization is generally oriented perpendicular to a substrate, and aprotective film, that are provided on a non-magnetic substrate, whereinthe orientation control film is made of a non-magnetic material whichcontains 33 to 80 at % of Ni and one or more kinds of elements selectedfrom Sc, Y, Ti, Zr, Hf, Nb and Ta.
 2. The magnetic recording mediumaccording to claim 1, wherein the orientation control film has an hcpstructure.
 3. The magnetic recording medium according to claim 1 or 2,wherein the orientation control film is made of at least one kindselected from the group consisting of NiTa alloy, NiNb alloy, NiTi alloyand NiZr alloy.
 4. The magnetic recording medium according to any one ofclaims 1 to 3, wherein a perpendicular magnetization anisotropy constantKu of the perpendicular magnetic film is equal to or higher than 1×10⁶erg/cc.
 5. The magnetic recording medium according to any one of claims1 to 4, wherein the perpendicular magnetic film has a compositioncontaining CoCrPt as the major constituent and also has a Cr contentequal to or higher than 16 and lower than 24 at % and a Pt content equalto or higher than 14 and lower than 24 at %, and a coercive force (Hc)is equal to or higher than 3000 (Oe), negative nucleation field (−Hn) isequal to or higher than 0 (Oe) and lower than 2500 (Oe), and a ratio ofresidual magnetization (Mr) to saturation magnetization (Ms), Mr/Ms, isequal to or higher than 0.9.
 6. The magnetic recording medium accordingto any one of claims 1 to 5, wherein a mean crystal grain diameter ofthe orientation control film is equal to or higher than 2 nm and lowerthan 20 nm.
 7. The magnetic recording medium according to any one ofclaims 1 to 6, wherein a thickness of the orientation control film isequal to or higher than 0.5 nm and lower than 20 nm.
 8. The magneticrecording medium according to any one of claims 1 to 7, wherein theperpendicular magnetization has a B content equal to or higher than 0.1at % and lower than 5 at % and Δθ50 is within a range from 2 to 10°. 9.The magnetic recording medium according to any one of claims 1 to 8,wherein a hard magnetic film made of a hard magnetic material isprovided between the non-magnetic substrate and the soft magneticundercoat film.
 10. A method of manufacturing a magnetic recordingmedium, which comprises forming at least a soft magnetic undercoat filmmade of a soft magnetic material, an orientation control film thatcontrols the orientation of a film provided right above, a perpendicularmagnetic film of which axis of easy magnetization is generally orientedperpendicular to a substrate, and a protective film, on a non-magneticsubstrate, while controlling so that the orientation control film ismade of a non-magnetic material which contains 33 to 80 at % of Ni andone or more kinds of elements selected from Sc, Y, Ti, Zr, Hf, Nb andTa.
 11. A magnetic read/write apparatus comprising a magnetic recordingmedium and a magnetic head that records information on the magneticrecording medium and plays the information, wherein the magneticrecording medium comprises at least a soft magnetic undercoat film madeof a soft magnetic material, an orientation control film that controlsthe orientation of a film provided directly thereabove, a perpendicularmagnetic film of which the axis of easy magnetization is generallyoriented perpendicular to a substrate, and a protective film, that areprovided on a non-magnetic substrate, while the orientation control filmis made of a non-magnetic material which contains 33 to 80 at % of Niand one or more kinds of elements selected from Sc, Y, Ti, Zr, Hf, Nband Ta.